Crystal manufacturing apparatus

ABSTRACT

A crystal manufacturing apparatus for manufacturing a group III nitride crystal includes a crucible that holds a mixed molten liquid including an alkali metal and a group III metal; a reaction vessel accommodating the crucible in the reaction vessel; a heating device that heats the crucible with the reaction vessel; a holding vessel having a lid that is capable of opening and closing, accommodating the reaction vessel and the heating device in the holding vessel; a sealed vessel accommodating the holding vessel in the sealed vessel, having an operating device that enables opening the lid of the holding vessel for supplying source materials into the crucible and taking out a manufactured GaN crystal under a sealed condition, and closing the lid of the holding vessel that is sealed in the sealed vessel, the sealed vessel including an inert gas atmosphere or a nitrogen atmosphere; and a gas supplying device for supplying a nitrogen gas to the mixed molten liquid through each of the vessels.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The disclosures herein generally relate to a crystal manufacturingapparatus, and more specifically to a crystal manufacturing apparatusfor manufacturing the group III nitride crystals.

2. Description of the Related Art

InGaAlN (a group III nitride semiconductor) related devices, used forlight sources such as ultraviolet, violet, blue, and green, arefabricated mostly on sapphire or silicon carbide (SiC) substrates usinga MOCVD (Metal Organic Chemical Vapor Deposition) method or a MBE(Molecular Beam Epitaxy) method and the like.

When a sapphire or a SiC substrate is used as a substrate forfabricating a group III nitride semiconductor, a large number of crystaldefects are introduced into the group III nitride semiconductor becauseof large differences in the lattice constant and the thermal expansioncoefficient between those substrates and a group III nitridesemiconductor. The crystal defects degrade the device characteristics.For an example, the crystal defects shorten the device lifetime andcause a larger current operation and the like, which relate directly todisadvantages of the devices.

Further, a sapphire substrate is an insulating material and it does notallow forming electrodes on it unlike a conventional substrate. Thisrequires forming electrodes on the group III nitride semiconductor; as aresult the area of a device becomes larger, which raises itsmanufacturing cost. As the device area becomes larger, there is adifferent problem arising as a wafer bending due to a combination ofhetero-materials of a sapphire substrate and a group III nitridesemiconductor.

Further, the group III nitride semiconductor device fabricated on asapphire substrate is difficult to be cleaved, so that forming mirrorfacets to provide a resonant cavity of a laser diode (LD) is notfacilitated. Thereby, presently, such resonant cavity facets are formedby using a dry etching technique or thinning the sapphire substrate tobe less than 100 μm thick with a polishing technique and scribing it foreasy cleaving. Thus, there is a difficulty forming resonant cavityfacets and cleaving chips in a single process unlike a conventional LDfabrication, which causes a high production cost due to complicatedfabrication processes.

Then, a technique is proposed where a group III nitride semiconductor isselectively, laterally grown on a sapphire substrate for reducingcrystal defects. This allows reducing crystal defects; however, theproblems due to non-conductivity of the sapphire substrate and adifficulty of cleaving still remain.

To solve such problems, a gallium nitride (GaN) substrate, the samematerial as a crystal to be grown, is most preferable as a substrate.For this reason, crystal growth techniques, such as gas phase growth andliquid phase growth are proposed for growing a bulk GaN crystal.However, a high quality GaN substrate with a large diameter forpractical use has not been achieved.

As a method obtaining a GaN substrate, a method of GaN crystal growthusing sodium (Na) flux is proposed (see reference 1). This methodutilizes sodium azide (NaN₃) and metallic Ga as source materials thatare placed in a reaction vessel (internal diameter: 7.5 mm, length: 100mm) made of a stainless steel that is sealed with nitrogen atmosphere;the reaction vessel is heated to a temperature ranging 600° C.-800° C.,and the temperature is maintained for a time period of 24-100 hours sothat and then a GaN crystal is grown.

This method allows growing a crystal at a relatively low temperature600° C.-800° C. with a relatively low pressure around 100 kg/cm² in thevessel. It may be characterized as a practical crystal growth condition.

Further, recently a high quality group III nitride crystal has beenachieved by reacting a mixed molten liquid of an alkali metal and agroup III metal with a group V source material containing nitrogen (seereference 2).

However, as a conventional flux method performs crystal growth under apressure ranging from several MPa to 10 MPa, a double wall vessel isused for separating functions of a pressure resistant and a heatresistant, and then a larger size inner vessel is developed for growinga larger size crystal (e.g. reference 2). In the case of a conventionalflux method, since alkali metals are used, a glove box controlling themoisture and oxygen concentration to be less than 1 ppm needs to be usedfor supplying the source materials of a group III metal and an alkalimetal into the inner vessel in the glove box. Thereby, the inner vesselis taken out from the outer vessel after every crystal growth cycle.During this time period the outer side of the inner vessel, the outervessel, and the parts between the outer vessel and the inner vessel areexposed to air. Thus heaters and thermal insulators as well any partslocated inside the outer vessel are exposed to air. Further, part of anitrogen gas introducing tube in the inner vessel is also exposed toair. Over the region exposed to air, moisture and oxygen are absorbedand desorbed when raising temperature of the region or introducingnitrogen gas into the region. As a result, the heaters and the thermalinsulators are degraded, and their impurities are contained in thesource materials so as to affect crystal growth. Further, in terms ofdetaching the inner vessel and parts associated with it, thereproducibility of thermal distribution becomes a problem. In addition,detaching and attaching the inner vessel or the parts cause time losswhich increases the production cost.

To avoid such problems, reference 3 suggests connecting an atmospherecontrol part to the space between a source weighting part and an outervessel of a crystal growth apparatus to prevent mixing the air.

Reference 4 suggests supplying alkali metal and a group III metal into acrucible in a inner vessel.

-   Reference 1 U.S. Pat. No. 5,868,837-   Reference 2 Japanese Patent Application Publication No. 2003-313099-   Reference 3 Japanese Patent Application Publication No. 2005-335983-   Reference 4 Japanese Patent Application Publication No. 2004-292286

In reference 3, however, the outer vessel is a pressure resident vessel,and it is difficult to provide a gate valve that connects to theatmosphere control part and allows source materials to pass through thegate valve at the same time.

Reference 4 shows that there is a need to open an inner vessel to takeout a grown crystal while there is no need to open the inner vessel whena source material is supplied.

What is needed is a crystal manufacturing apparatus that grows a groupIII nitride crystal without exposing parts inside of the outer vessel toair while avoiding detachment of an inner vessel.

SUMMARY OF THE INVENTION

It is a general object of at least one embodiment of the presentinvention to provide a crystal manufacturing apparatus that enablesgrowing a group III nitride crystal without exposing parts inside of theouter vessel to air while avoiding detachment of an inner vessel.

In one embodiment, a crystal manufacturing apparatus for manufacturing agroup III nitride crystal includes a crucible that holds a mixed moltenliquid including an alkali metal and a group III metal, a reactionvessel accommodating the crucible in the reaction vessel, a heatingdevice that heats the crucible with the reaction vessel, a holdingvessel having a lid that is capable of opening and closing,accommodating the reaction vessel and the heating device in the holdingvessel, a sealed vessel accommodating the holding vessel in the sealedvessel, having an operating device that enables opening the lid of theholding vessel for supplying source materials into the crucible andtaking out a manufactured GaN crystal under a sealed condition, andclosing the lid of the holding vessel that is sealed in the sealedvessel, wherein the sealed vessel includes an inert gas atmosphere or anitrogen atmosphere in the sealed vessel, and a gas supplying device forsupplying a nitrogen gas to the mixed molten liquid through each of thevessels.

In one embodiment, a crystal manufacturing apparatus for manufacturingthe group III nitride crystals includes a crucible that holds a mixedmolten liquid that includes an alkali metal and a group III metal, areaction vessel accommodating the crucible in the reaction vessel, aheating device that is positioned at a predetermined relative locationrelative to the crucible, and heats the crucible through the reactionvessel, a sealed vessel accommodating the holding vessel in the sealedvessel, having an operating device that enables opening the lid of theholding vessel for supplying source materials into the crucible andtaking out a manufactured GaN crystal under a sealed condition, andclosing the lid of the holding vessel that is sealed in the sealedvessel, wherein the sealed vessel includes an inert gas atmosphere or anitrogen atmosphere in the sealed vessel, a gas supplying device forsupplying a nitrogen gas to the mixed molten liquid through each of thevessels, and a transfer mechanism that allows for the sealed vessel tobe transferred relative to the reaction vessel and the heating device,or the reaction vessel and the heating device to be transferred relativeto the sealed vessel, wherein the relative position between the reactionvessel and the heating device to be maintained, and the transfermechanism providing the reaction vessel in the sealed vessel to bepositioned at a first position when crystal growth is performed, and thereaction vessel in the sealed vessel to be positioned at a secondposition which is different from the first position when the sourcematerials are supplied or the group III crystal is taken out.

According to the first or second a crystal manufacturing apparatus ofthe present invention, each of the crystal manufacturing apparatuses iscapable of supplying the source materials and taking out themanufactured group III crystals without exposing the crucible, thereaction chamber, and the heating device to air. Thus it becomespossible to prevent exposing the parts inside of the outer vessel to airand manufacture the group III nitride crystals while avoiding detachmentof an inner vessel. Then, it is possible to manufacture high quality GaNcrystals continuously as well as efficiently without degradation ofparts of the manufacturing apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and further features of embodiments will become apparentfrom the following detailed description when read in conjunction withthe accompanying drawings, in which:

FIG. 1 is a schematic diagram of a crystal manufacturing apparatus in aview of cross section relating to a first embodiment of the presentinvention;

FIGS. 2A and 2B are enlarged views of the end of a holding device shownin FIG. 1;

FIG. 3 is a schematic diagram for explaining a structure of an up/downmechanism shown in FIG. 1;

FIG. 4 shows a timing chart of signals detected by an oscillationdetecting device;

FIG. 5 is a timing chart indicating changes in temperatures of acrucible and a GaN crystal;

FIGS. 6A and 6B are schematic diagrams for explaining the changes ineach condition of source materials in a crucible;

FIG. 7 is a schematic diagram for explaining the condition of thecrucible and the inside of the reaction vessel at a timing t2 indicatedin FIG. 5;

FIG. 8 is a graph for explaining the relationship between temperaturesof a GaN crystal and flow rates of nitrogen gas;

FIG. 9 is a graph for explaining the relationship between the pressuresof nitrogen gas and the temperature of crystal growth for growing a GaNcrystal;

FIG. 10 is a flowchart for explaining a manufacturing method of a GaNcrystal using the crystal manufacturing apparatus in FIG. 1;

FIGS. 11A and 11B are schematic diagrams for explaining a growingprocess of a GaN crystal;

FIG. 12 is a schematic cross-sectional diagram of a crystalmanufacturing apparatus related to a second embodiment of the presentinvention;

FIG. 13 is a schematic diagram for explaining the transfer of the sealedvessel;

FIG. 14 is a flowchart for explaining the method of GaN crystal growthusing the crystal manufacturing apparatus shown in FIG. 12;

FIG. 15 is a schematic diagram for explaining a modified example of thecrystal manufacturing apparatus of FIG. 12;

FIG. 16 is a schematic cross-sectional diagram of a crystalmanufacturing apparatus related to a third embodiment;

FIGS. 17A-17D are diagrams for explaining identical component parts usedin a second embodiment;

FIG. 18 is a schematic diagram for explaining gloves provided in thesealed vessel of FIG. 16;

FIG. 19 is a schematic diagram (step 1) for explaining the operationalprocedure when source materials are supplied into the crystalmanufacturing apparatus of FIG. 16;

FIG. 20 is a schematic diagram (step 2) for explaining the operationalprocedure when source materials are supplied into the crystalmanufacturing apparatus of FIG. 16; and

FIG. 21 is a schematic diagram for explaining a crystal manufacturingsystem related to a fourth embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

A first embodiment according to the present invention will be describedby referring to FIG. 1-FIG. 11B. FIG. 1 shows a schematic diagram of acrystal manufacturing apparatus 100 related to a first embodiment of thepresent invention.

This crystal manufacturing apparatus 100 is for manufacturing a GaNcrystal manufactured by supplying nitrogen gas to a mixed molten liquidthat includes metallic sodium (Na) and metallic gallium (Ga). Thus, thecrystal manufacturing apparatus 100 manufactures a GaN crystal by a fluxmethod.

The crystal manufacturing apparatus 100 comprises a crucible 10, areaction vessel 20, a bellows 30, a holding device 40, heating devices(50, 60), temperature sensors (51, 61), gas supplying tubes (90, 200), apressure control device 120, gas cylinders (130, 220), a gaspurification apparatus 160, pipes (140, 150, 180), a thermocouple 190, aflow meter 210, an oscillation device 230, an up/down mechanism 240, anoscillation detecting device 250, a temperature control device 260, aholding vessel 300, a base flange 310, and a sealed vessel 400.

Each gas cylinder (130 and 220) is filled with nitrogen gas.

The crucible 10 is constructed of boron nitride (BN) with a circularcontour or made of austenitic stainless steel (“SUS316L”). The crucible10 holds a mixed molten liquid 270 including metallic Na and metallicGa, and is accommodated in a reaction vessel 20.

The reaction vessel 20 comprises a body part 21, a lid part 22, and apipe connecting part 23. The body part 21, the lid part 22, and the pipeconnecting part 23 are made from SUS316L. A gap between the body part 21and the lid part 22 is sealed with a metallic O-ring. Further, the pipeconnecting part 23 is provided at the bottom plane of the body part 21.

The bellows 30 is connected to the lid part 22 of the reaction vessel 20in the gravitational direction DR1. The bellows 30 holds the holdingdevice 40 and seals the reaction vessel 20 from the outer part of it.Further, the bellows 30 stretches or shrinks in the gravitationaldirection DR1 with the holding device 40 transferring in thegravitational direction DR1.

The heating device 50 is placed to surround an outer surface 20A of thereaction vessel 20. The heating device 50 comprises a heater and acurrent source, in which a current determined by a control signal CTL1of the temperature control device 260 is supplied from the currentsource to the heater.

The heating device 60 is placed to face a bottom 20B of the reactionvessel 20. The heating device 60 comprises another heater and anothercurrent source, in which a current determined by a control signal CTL2of the temperature control device 260 is supplied from the currentsource to the heater

The temperature sensor 51 is placed close to the heating device 50,detects a temperature (T1) of the heating device 50, and outputs thedetected result to the temperature control device 260.

The temperature sensor 61 is placed close to the heating device 60,detects a temperature (T2) of the heating device 60, and outputs thedetected result to the temperature control device 260.

For the gas supplying tube 90, one end is connected to the pipeconnecting part 23 of the reaction vessel 20, and the other end isconnected to the gas cylinder 130. In part of the gas supplying tube atthe side of the pipe connection part 23, a metallic Na molten liquid 280is held.

The pressure control device 120 is provided in the way (the gas cylinder130 side) of the gas supplying tube 90 and adjusts the pressure ofnitrogen gas flowing from the gas cylinder 130 at a predeterminedpressure.

As an example, the holding vessel 300 made of SUS316L accommodates thereaction vessel 20, the holding device 40, the heating devices (50, 60),and the temperature sensors (51, 61) in it. The holding vessel 300comprises a body part 301 and a base part 302. The body part 301 and thebase part 302 are connected with a metallic O-ring and bolts (notshown). The base part 302 is fixed on a base flange 310. Further, theholding vessel 300 is cooled with cooling water and is apressure-resistant vessel capable of operating high pressure.

The sealed vessel 400, for example, is made of SUS316L and accommodatesthe base flange 310 and the holding vessel 300. The sealed vessel 400includes at least a pair of gloves (not shown) so that an operator canuse them for work in the sealed vessel 400. Therefore, the sealed vessel400 functions as a glove box. The inside of the sealed vessel isisolated from air and maintains a high purity nitrogen atmosphere.

The sealed vessel 400 comprises a source reserve chamber (not shown) forreserving metallic Na and metallic Ga and a crystal storage chamber (notshown) for storing fabricated GaN crystal. The source reserve chamberincludes a supplement mechanism that is capable of supplying sourcematerials into the source reserve chamber from the outside of the sealedvessel 400 almost without changing the atmosphere in the sealed vessel400.

The crystal storage chamber includes a take-out mechanism that iscapable of taking out GaN crystal stored in the storage chamber to theoutside of the sealed vessel 400 almost without changing the atmospherein the sealed vessel 400.

The base flange 310 is fixed on a basal plane of the sealed vessel 400.

The gas purification apparatus 160 is connected to the sealed vessel 400through the pipe 140 and the pipe 150. The gas purification apparatus160 removes impurities such as oxygen and moisture included in gas takenfrom the sealed vessel 400 through the pipe 140 and returns the gas tothe sealed vessel 400 through the pipe 150. Thereby, the concentrationof oxygen and moisture of the gas in the sealed vessel 400 is maintainedat less than 1 ppm.

For example, the oscillation device 230 includes a piezoelectric devicethat applies oscillations at a predetermined frequency for the holdingdevice 40.

As an example, the oscillation detecting device 250 includes anacceleration pick-up device to detect the oscillation of the holdingdevice 40, and outputs the detected results to the up/down mechanism 240as an oscillation detected signal.

One end of the gas supplying tube 200 is connected to the pipe 180 andthe other end of that is connected to the gas cylinder 220 through theflow meter 210.

The gas flow meter 210 adjusts the flow rate of the nitrogen gas fromthe gas cylinder 220 to a predetermined flow rate according to a controlsignal CTL3 of the temperature control device 260.

As an example, an enlarged view of the parts of the holding device 40,the pipe 180, and the thermocouple 190 is shown in FIG. 2A and FIG. 2B.

The holding device 40 includes a cylindrical part 41. One end of thecylindrical part 41 is inserted into a space 24 in the reaction vessel20 through an opening provided in the lid part 22 of the reaction vessel20. Further, a seed crystal 5 is attached on the bottom plane 41Boutside of the cylindrical part 41 (see, FIG. 2A). A GaN crystal 6including the seed crystal 5 grows on the bottom plane 41B of thecylindrical part 41 (see FIG. 2B). The holding device 40 holds the grownGaN crystal 6.

The pipe 180 has a round-shaped cross section and is positioned in thecylindrical part 41 of the holding device 40. Further, the bottom 180Aof the pipe 180 is positioned to face the bottom plane 41B of thecylindrical part 41. Plural holes 181 are formed through the bottom 180Aof the pipe 180.

Nitrogen gas from the gas cylinder 220 having a flow rate adjusted bythe flow meter 210 is supplied to the inside of the holding device 40and flows through the plural holes 181 to the bottom 41B of thecylindrical part 41. Thereby, the seed crystal 5 and the GaN crystal 6are cooled.

Further, the nitrogen gas flowing in the cylindrical part 41 flows outof the crystal manufacturing apparatus 100 through openings provided inthe cylindrical part 41, which openings are not shown in the figure.

For the thermocouple 190, an end 190A is positioned in the cylindricalpart 41 to contact the bottom plane 41B. The thermocouple 190 detectsthe temperature (temperature T3) of the seed crystal 5 or the GaNcrystal 6 and outputs the detected result to the temperature controldevice 260.

The up/down mechanism 240 is placed on the holding device 40 at theupper side of the bellows 30. The up/down mechanism, as shown in FIG. 3as an example, includes a concavo-convex part (rack) 241, a gear 242, ashaft part 243, a motor 244, and a control part 245.

The concavo-convex part 241 has a triangular shaped cross section and isfixed on the outer surface 41A of the cylindrical part 41. The gear 242is fixed on one end of the shaft part 243 and placed to engage with theconcavo-convex part 241.

On the shaft part 243, one end is joined with the gear 242 and the otherend joined with the shaft (not shown) of the motor 244. The motor 244turns the gear 242 to in the direction of an arrow 246 or an arrow 247according to the indication of the control part 245.

The control part 245 controls the motor 244 for turning the gear 242 inthe direction of the arrow 246 or the arrow 247 according to anoscillation detection signal BDS of the oscillation detecting device250.

The holding device 40 is moved upward in the gravitational direction DR1when the gear 242 turns in the arrow 246 direction, and the holdingdevice 40 is moved downward in the gravitational direction DR1 when thegear 242 turns in the direction of the arrow 247.

For examples a timing chart of the oscillation detection signal BDS isshown in FIG. 4. As the holding device 40 is widely oscillated due tooscillation applied by the oscillation device 230 when the holdingdevice 40 does not touch the mixed molten liquid 270, the oscillationdetection signal BDS shows a relatively large signal wave SS1. (B) Theoscillation detection signal BDS becomes a relatively small signal waveSS2, since the holding device 40 is not oscillated widely for theoscillation applied by the oscillation device 230 due to the viscosityof the mixed molten liquid 270 when the holding device 40 is touchingthe mixed molten liquid 270. (C) When part (or GaN crystal 6) of theholding device 40 is immersed in the mixed molten liquid 270, the effectof the viscosity becomes larger, so that it becomes more difficult forthe holding device 40 (or GaN crystal 6) to be oscillated by theoscillation applied by the oscillation device 230. As a result, theoscillation detection signal BDS shows that the amplitude of the signalwave SS3 is smaller than that of the signal wave SS2.

During growing a crystal, the control part 245 detects the signal waveof the oscillation detection signal BDS for every predetermined timing.When the detected signal wave is SS1, the control part 245 controls themotor 244 for moving the holding device 40 downward in the gravitationaldirection DR1 until the detected signal wave becomes SS2 or SS3.

Further, the control part 245 controls the motor 244 to stop turning thegear 242 when the signal wave of the oscillation detection signal BDSbecomes SS2 or SS3. Thereby, during crystal growth, one end of theholding device 40 can be maintained in a gas-liquid interface 2 or theone end of the holding device 40 can be maintained in the mixed moltenliquid 270.

The temperature control device 260 generates a control signal CTL1 basedon the temperature T1 for heating the crucible 10 and the reactionvessel 20 at the temperature of crystal growth, and generates a controlsignal CTL2 based on the temperature T2 for heating the crucible 10 andthe reaction vessel 20 at the temperature of crystal growth. Further,the temperature control device 260 generates the control signal CTL3based on the temperature T3 for supplying nitrogen gas with a properflow rate to control the temperature of the seed crystal 5 or the GaNcrystal 6 to be lower than the temperature of crystal growth.

Further, the temperature control device 260 outputs the generatedcontrol signal CTL1 to the heating device 50, the control signal CTL2 tothe heating device 60, and the control signal CTL3 to the flow meter210.

Fabrication Method of GaN Crystal

Fabrication method using the crystal manufacturing apparatus 100 of theconstruction shown above will be explained by referring to FIG. 5-FIG.11B. FIG. 5 is a timing chart showing the changes in temperatures of thecrucible 10 and GaN crystal 6. FIG. 5 shows that the thick line k1indicates the change in the temperature of the crucible 10, and thinlines k2 and k3 indicate the temperature of the GaN crystal 10 for twocases (Case A and Case B). Further, a flow chart in FIG. 10 shows thesequence of operations by an operator.

(1-1) Within the sealed vessel 400, use a pair of gloves installed atthe sealed vessel 400 and take off a bolt (not shown) connecting thebody part 301 and the base part 302.

(1-2) In the vessel 400, open the holding vessel 300 by moving the bodypart 301 of the holding vessel 300 upward.

(1-3) In the sealed vessel 400, open the reaction vessel 20 by removingthe lid 22 of the reaction vessel 20 (step s1). Under that condition,the atmosphere in the sealed vessel 400 is a nitrogen gas atmosphere oran inert gas (such as Argon) atmosphere, and the inner pressure has apositive pressure by 0.1 atmospheric pressure compared to theatmospheric pressure. In that case, the inner atmosphere of the sealedvessel 400 is nitrogen gas or an inert gas (such as Argon), and theinner pressure is a positive pressure of about 0.1 atmospheric pressureabove the atmospheric pressure.

(1-4) In the sealed vessel 400, take out a metallic Na and a metallic Gafrom the source reserve chamber and supplys them into the crucible 10with a ratio of amounts 1:1 (Step S2). Further, attach the seed crystal5 onto the one end of the holding device 40 (See FIG. 11A).

(1-5) In the sealed vessel 400, attach the lid part 22 of the reactionvessel 20 to the body part 21.

(1-6) In the sealed vessel 400, move the body part 301 of the holdingvessel 300 downward, and place the body part 301 on the base part 302.Then connect the body part 301 and the base part 302 with the bolt.Thereby, the reaction vessel 20 and the holding vessel 300 can be closedwithin the sealed vessel 400 (Step S3).

(1-7) Introduce nitrogen gas through the gas supplying tube 90 until thepressure in the reaction vessel 20 and the gas supply tube reaches 1.01MPa (Step S4). In a case where the inner atmosphere of the sealed vessel400 is not a nitrogen gas atmosphere in the step 1, perform purging withnitrogen gas to replace with it.

(1-8) Heat the crucible 10 through the reaction vessel 20 by using eachheating device (50, 60) (Step S5). In the present case, the temperatureof crystal growth is 800° C.

The metallic Na 7 and the metallic Ga 8 in the crucible 10 are solidstate before the crucible 10 is heated. When the temperature of thecrucible 10 reaches approximately 30° C., the metallic Ga 8 becomesliquid state.

Further, when the temperature of the crucible 10 reaches 98° C. (timingt1 in FIG. 5), the metallic Na 7 in the crucible 10 becomes liquid stateand mixes with the metallic Ga 8 that is melted previously. Thereafter,a metallic compound of Ga and Na is formed, and the metallic compoundbecomes a mixed molten liquid 270 at a temperature of 560° C. (See FIG.6B). Further the pressure of the nitrogen gas 4 is adjusted by thepressure control device 120, and the nitrogen gas 4 is supplied into thespace 24 through the gas supplying tube 90 (See FIG. 7).

During the process where the crucible 10 is heated up to 800° C., thevapor pressure of the metallic Na evaporated from the mixed moltenliquid 270 becomes gradually higher, and the evaporated metallic Nastays in a low temperature part of the gas supplying tube 90 as a moltenliquid metallic Na 280.

In the region of the gas supplying tube 90 where the metallic Na moltenliquid stays, the temperature is maintained by a heater (not shown) at aproper temperature to maintain the metallic Na in liquid state forpreventing its actual evaporation. The actual temperature of metallic Nafor preventing evaporation is, for example, 200˜300° C.

The vapor pressure of Na at 200° C. is approximately 1.8×10⁻² Pa and 1.8Pa at 300° C. Thereby, this can reduce a fluctuation of the mixtureratio of metallic Na and metallic Ga in the mixed molten liquid 270.

(1-9) When the temperature of the crucible 10 reaches 800° C. (timing t2in FIG. 5), immerse the seed crystal 5 into the mixed molten liquid 270by using the up/down mechanism 240 (Step S6).

Under a high temperature condition where the temperature of the crucible10 is approximately 800° C., the nitrogen gas 4 in the space 24 isincorporated into the mixed molten liquid 270 via the metallic Naplaying as mediator. A nitrogen concentration or a concentration ofGa_(x)N_(y) (x, y are real numbers) in the mixed molten liquid 270 ismaximum at around the interface of gas-liquid 2, so that the GaN crystal6 is grown from the seed crystal 5 (See FIG. 11B). Under this condition,the temperature of the crucible 10 and the nitrogen gas pressure in thereaction vessel 20 correspond to a temperature and a pressure in aregion REG3 as indicated in FIG. 9.

FIG. 9 shows that REG1 is a region where a GaN crystal is melted. REG2is a region where a large number of self-nucleation is formed on abottom and a side surface of that contacts with the mixed molten liquid270 in the crucible 10, and columnar GaN crystals are grown in a C-axis(<0001>) direction. REG3 is a region where a GaN crystal grows from theseed crystal.

(1-10) For a predetermined time period (several hours), the temperatureof the crucible 10 is held at 800° C. (Step S7).

(1-11) Once the crystal growth of a GaN crystal starts, nitrogen gas issupplied into the pipe 180 and cools the GaN crystal 6 to be lower thanthe temperature (=800° C.) of the mixed molten liquid 270 (Step S8) toincrease the degree of supersaturation of the nitrogen in the mixedmolten liquid 270 or Ga_(x)N_(y) (real numbers x, y) near the GaNcrystal 6. Thereby, the crystal growth of the GaN crystal 6 ismaintained.

When the temperatures T1 and T2 reach 800° C.+α° C., two methods areconsidered; method A is that the temperature of GaN crystal 6 is reducedto Ts1 (e.g. 790° C.) and maintained at the temperature (Case A) asindicated with a thin line k2 in FIG. 5; method B is that thetemperature of the GaN crystal 6 is gradually reduced toward thetemperature Ts2 (e.g., 750° C.) as indicated with a thin line k3 in FIG.5 (Case B). The temperature, 800° C.+α° C., indicates the temperature ofheaters used in each heating device (50, 60) to increase a temperatureof the crucible 10 to 800° C. The temperature control device 260 isprogrammed for response to either the method A or the method B.

More particularly, for the method A, when the temperature T1 andtemperature T2 reach 800° C.+α° C., the temperature control device 260immediately generates a control signal CTL3 and outputs it to the flowmeter 210 for supplying a proper flow rate fr1 (sccm) of nitrogen Gasthrough the flow meter 210 to control the temperature of the GaN crystal6 to be Ts1. Thereby, the temperature of the GaN crystal 6 decreases ina short period of time and becomes constant at a temperature of Ts1.

Further, for the method B, when the temperature T1 and temperature T2reach 800° C.+α° C., the temperature control device 260 generates acontrol signal CTL3 and outputs it to the flow meter 210 for graduallyincreasing the flow rate of the nitrogen gas in a predetermined periodof time from a flow rate 0 to a flow rate fr2 (sccm) (See FIG. 8).Thereby, the temperature of the GaN crystal 6 is gradually reducedtoward t the temperature of Ts2.

While the crystal growth of GaN is proceeding, the nitrogen gas in thespace 24 is consumed; as a result the nitrogen gas in the space 24 isdecreased. Then a pressure P1 in the space 24 becomes lower than apressure P2 in the gas supplying tube 90 on the side of the pressurecontrol device 120 (P1<P2), and the nitrogen gas in the gas supplyingtube 90 (the side of the pressure control device 120) is supplied intothe space 24 through the molten liquid metallic Na 280. Thus, thenitrogen gas is supplied in to the space 24 (Step S9).

(1-12) Move the GaN crystal 6 to put the GaN crystal 6 with the mixedmolten liquid 270 (Step S10). Thereby, the GaN crystal 6 in contactgrows to a large size.

(1-13) After passing a predetermined period of time (timing t4 in FIG.5), heating using each heating device (50, 60) is stopped. Thereby, thetemperature of the crucible 10 is reduced (Step S11).

(1-14) When the temperature of the crucible 10 and the reaction vessel20 reach room temperature, the same operational sequence described above(1-1)˜(1-3) is performed.

(1-15) Take the GaN crystal out of the crucible 10, and put it in thecrystal store chamber (Step S12).

(1-16) The same operational sequence as described above (1-4)˜(1-7) isperformed, and preparation for a next run of GaN crystal growth isperformed.

(1-17) The same operational sequence as described above (1-8)˜(1-15) isperformed for manufacturing a GaN crystal.

After this, the same operational sequences as (1-16) and (1-17) arerepeatedly performed when necessary.

When the amounts of the metallic Na and metallic Ga reserved in a sourcestore chamber (not shown) are decreased, the operator supplies themetallic Na and metallic Ga to the source store chamber from the outsideof the sealed vessel 400 with a supply mechanism almost without changingthe atmosphere in the sealed vessel 400.

Further, it is possible for the operator to take the GaN crystal storedin the crystal store chamber (not shown) out of the sealed vessel 400using a take-out mechanism (not shown) almost without changing theatmosphere in the sealed vessel 400.

As described above, for the crystal manufacturing apparatus 100 relatedto the first embodiment of the present invention, “a gas supplyapparatus” comprises a gas supplying tube 90, a pressure control device120, and a gas cylinder 130.

Further, “a method of operation” includes at least a pair of gloves.

As described above, according to the crystal manufacturing apparatus 100relating to the first embodiment of the present invention, it enablessupplying source materials (metallic Ga and metallic Na) into thecrucible 10, and taking the manufactured GaN crystal out of the crucible10 in the sealed vessel 400 filled with nitrogen gas. Thus,manufacturing a GaN crystal can be performed without exposing parts suchas each heating device (50, 60) in the holding vessel 300 to air. Then,it is possible to manufacture high quality GaN crystals continuously aswell as efficiently without degradation of parts of the manufacturingapparatus.

There is no need of a preliminary gas purge to prevent releasingimpurity gases from the comprising parts of the manufacturing apparatus,and it enables shortening the operating time. Thereby, this allowsmanufacturing products at lower cost.

Further, moving the reaction vessel 20 becomes unnecessary, and thisallows preventing changes in relative position between the reactionvessel 20 and each heating device (50, 60). Thereby, it becomes possibleto perform crystal growth maintaining the same conditions. Thus, itenables manufacturing the same quality of GaN crystals constantly.

Second Embodiment

A second embodiment according to the present invention is explained byreferring FIG. 12-FIG. 14. FIG. 12 shows a schematic diagram of acrystal manufacturing apparatus 100A related to the second embodiment ofthe present invention.

The crystal manufacturing apparatus 100A utilizes a sealed vessel 500instead of the holding vessel 300 and the sealed vessel 400 of thecrystal manufacturing apparatus 100 that is previously described above,and the sealed vessel 500 is modified to be capable of moving upward ordownward in gravitational direction DR1 relative to “the crucible 10,the reaction vessel 20, the holding device 40, the heating devices (50,60), and the temperature sensors (51, 61).” Further, in the following,the present embodiment is mainly described based on the differences fromthe first embodiment and uses identical symbols for previously explainedcomponent parts; therefore descriptions for such symbols are simplifiedor omitted.

In the following, a part that is comprised of the crucible 10, thereaction vessel 20, the holding device 40, the heating devices (50, 60),and the temperature sensors (51, 61) is named “an inner device.”

The sealed vessel 500 includes a vessel placing space 501 and a spaceformation part 502. The vessel placing space 501 includes a bell shape,and the space formation part 502 includes a cylindrical external shape.Further, the vessel placing space 501 is placed on the space formationpart 502. The vessel placing space 501 and the space formation part 502are made of SUS316L and fabricated in one body. Further, the vesselplacing space 501 and the space formation space 502 are pressureresistant vessels.

The vessel placing space 501 is fixed on a supporting part (not shown)that is vertically movable in the gravitational direction DR1. Thereby,the sealed vessel 500 is transferred (moved) in the gravitationaldirection DR1 as the supporting part moves vertically in thegravitational direction.

Further, the space formation part 502 comprises an upper part 5021, avertical part 5022, and a base part 5023. There is a stage 600 insidethe space formation part 502 which is fixed on a floor with supportingpoles 700 that penetrate the base part 5023 of the space formation part502 and stands on the floor. Thus, the stage 600 is not transferred whenthe sealed vessel 500 is transferred.

The inner device described above is placed on the stage 600. Then, theinner device is not transferred when the sealed vessel 500 istransferred.

At the lowest level of the sealed vessel 500, the stage 600 contacts theupper part 5021 via an O-ring 503. Then, the stage 600 and the upperpart 5021 can be connected with bolts (507, 508). Further, the stage 600contacts the vertical part 5022 via an O-ring 505. Therefore, the spacesbelow the stage 600 and above the stage 600 are separated due to sealingby the O-ring 505 when the sealed vessel 500 is transferred.

The gas purification apparatus provides a high purity nitrogenatmosphere via piping 1140 and piping 1150.

There are a transparent window (not shown) and at least a pair of gloves(not shown) in the space formation part 502 for enabling an operator towork in the space formation part 502. Thus, the space formation part 502provides a function as a glove box.

Gases in the vessel placing space 501 can be evacuated by a vacuum pump330 through an evacuating tube 320. In the pathway of the evacuatingtube 320 is included an open/close valve 340.

A gas cylinder 410 is filled with nitrogen gas. The nitrogen gas fromthe gas cylinder 410 is supplied into the vessel placing space 501 via agas supplying tube 350 after having its pressure controlled by apressure control device 370 and supplied into the space formation part502 via the gas supplying tube 350 and a gas supplying tube 380. In thepathway of the gas supplying tube 350 is provided an open/close valve360, and an open/close valve 390 is provided in the pathway of the gassupplying tube 380.

Gases in the space formation part 502 can be evacuated with a vacuumpump 530 through an evacuating pipe 540. An open/close valve 550 isprovided in the pathway of the evacuating pipe 540.

A source material storage chamber 580 is attached with the vertical part5022. The inside of the source material storage chamber 580 ismaintained with a nitrogen gas atmosphere, and metallic Ga and metallicNa are stored in it. The source material storage chamber 580 includes asource supplying entrance (not shown) between the space formation part502 and itself.

Further, the vertical part 5022 is attached to a crystal storage chamber590. The inside of the crystal storage chamber 590 is maintained with anitrogen atmosphere, and a GaN crystal taken from the crucible 10 isstored in it. The crystal storage chamber 590 includes a take-out gate(not shown) between the space formation part 502 and itself.

The source material storage chamber 580 and the crystal storage chamber590 allow evacuating gas and exchanging gas such as high purity nitrogengas or argon gas by using an evacuation pump (not shown).

The gas supplying tube 90 is connected with a pipe connecting part 23through a base part 5023 of the sealed vessel 500 and the stage 600 bypenetrating.

Method of Manufacturing GaN Crystal

A method of manufacturing a GaN crystal utilizing the crystalmanufacturing apparatus 100A constructed as described above is explainedby referring FIG. 14. A flowchart of FIG. 14 shows procedures oroperation to be performed by an operator. The flowchart of FIG. 14 ismodified by replacing the steps S1-S3 and the steps S12-S14 with thesteps S21-S23 with the steps S24-S27.

(2-1) Transfer the sealed vessel 500 upward by a holding part (notshown). Thereby, the space 5025 is formed in the space formation part502 (step S21).

As the volume of space 5024 in the space formation part 502 decreaseswith transferring of the sealed vessel 500, the evacuation pump 530evacuates nitrogen gas gradually to maintain the pressure in the space5024 to be 0.1 MPa+α. Further, as the volume in the space of the vesselplacing space 501 increases with transferring of the sealed vessel 500,the pressure control device 370 supplies nitrogen gas into the vesselplacing space 501 to maintain the pressure in the vessel placing space501 to be 0.1 MPa+α. Thus, the sealed vessel 500 is transferred whilemaintaining the pressure balance of the vessel placing space 501 and thespace formation part 502.

When the stage 600 contacts the base part 5023 of the sealed vessel 500(see FIG. 13), the sealed vessel 500 stops being transferred. Then, the“inner device” is located in a position lower than a position of theupper part 5021 of the space formation part. This position of thereaction vessel 20 is defined as “a second position.”

(2-2) Using the gloves provided in the sealed vessel 500, remove the lid22 of the reaction vessel 20 from the body part 21 in the space 5025with nitrogen a gas atmosphere.

(2-3) Take the metallic Ga and the metallic Na out of the sourcematerial storage chamber 580 through the source supplying entrance.Further, attach the seed crystal 5 on the one end of the holding device40.

(2-4) Close the reaction vessel 20 by assembling the lid 22 onto thebody part 21.

(2-5) Transfer the sealed vessel 500 downward using the supporting part(not shown) (step S23).

The volume of the space above the stage 600 decreases with transferringof the sealed vessel 500, so that the evacuation pump 330 evacuatesnitrogen gas gradually to maintain the pressure in the space above thestage 600 to be 0.1 MPa+α through the valve 340. Further, the volume ofthe space 5024 below the stage 600 increases with transferring of thesealed vessel 500, so that the pressure control device 370 suppliesnitrogen gas gradually into the space 5024 to maintain the pressure inthe space 5024 to be 0.1 MPa+α.

When the stage 600 contacts with the upper part 5021, the sealed vessel500 stops transferring. At this point, the “inner device” is located inthe vessel placing part 501 that is above the space formation part 502.This position of the reaction vessel is defined as “a first position.”

(2-6) Perform operation in the same way of the steps S4-S11 above.

(2-7) When the temperature of the crucible 10 and the reaction vessel 20reaches room temperature, perform operations in the same as the steps(2-1) and (2-2) above (step S24). (2-8) Take the GaN crystalmanufactured out of the crucible 10, put it in the crystal storagechamber 590 (step S25).

(2-9) Perform the same operations of steps (2-3)-(2-5), and prepare thesucceeding operations of GaN crystal manufacture (step S26, step S27).

(2-10) Perform the same operations of steps of (2-6)-(2-8), andmanufacture a GaN crystal.

In the following, repeat the same operations of steps of (2-9) and(2-10) above when necessary.

As described above, in the second embodiment related to the crystalmanufacturing apparatus 100A of the present invention, “gas supplyingdevice” comprises the gas supplying tube 90, the pressure control device120, and the gas cylinder 130.

Further, “a method of the operation” comprises at least using a pair ofgloves.

Further, “a transfer mechanism” comprises the supporting part (notshown).

Further, “a pressure control device” comprises the evacuation pumps(330, 530), the evacuating tubes (320, 540), and the open/close valves(340, 360, 390, 550), the gas cylinder 410, the pressure control device370, and the gas supplying tubes (350, 380).

As explained above, according to the second embodiment related to thecrystal manufacturing apparatus 100A, the operation comprisestransferring the sealed vessel 500 upward, forming the space 5025 withnitrogen a gas atmosphere in the space formation part 502, utilizinggloves in the space 5025, supplying sources (metallic Ga and metallicNa) into the crucible 10, and taking out the manufactured GaN crystalfrom the crucible 10. Thereby, it enables manufacturing a GaN crystalwhile preventing exposure of “the inner device” to air. Thus, a similareffect of the first embodiment above can be obtained.

Further, for the second embodiment above, for example, a pressureadjusting valve may be provided on the stage 600 instead of the above“pressure control device” to enable transferring nitrogen gas betweenthe space formed above the stage 600 and the space formed below thestage 600 so that the pressures in the two spaces are equally balancedwhile the sealed vessel 500 is being transferred vertically.

Further, for example, in a crystal manufacturing apparatus 100B shown inFIG. 15, instead of the above “pressure control device”, the pressuremay be adjusted by utilizing the piping 610 and the pressure adjustingvalve 620 for equally balancing the pressures of the space formed abovethe stage 600 and the space formed below the stage 600 while the sealedvessel 500 is being transferred vertically.

For the piping 610, one end is connected to the vessel placing part 501and the other end is connected to the space formation part 502. Thepressure adjusting valve 620 is provided in the pathway of the piping610 and equally balances the pressures in the vessel placing space 501and the space formation part 502.

Further, the crystal manufacturing apparatus 100A and the crystalmanufacturing apparatus 100B may provide gas purification apparatusesfor supplying inert gas or nitrogen gas containing amounts of moistureand oxygen below 1 ppm into the space formation part 502.

Third Embodiment

A third embodiment of the present invention is explained by referringFIG. 16-FIG. 20. FIG. 16 shows a schematic diagram of a crystalmanufacturing apparatus 100C related to the third embodiment of thepresent invention.

The crystal manufacturing apparatus 100C provides a crucible 10, areaction chamber 20, a holding device 40, heating devices (50, 60),temperature sensors (51, 61), a sealed vessel 3000, and a gas supplyingdevice (not shown) that is similar to the “gas supplying device”described above.

A “inner device” comprising the crucible 10, the reaction vessel 20, theholding device 40, the heating devices (50, 60), and the temperaturesensors (51, 61) is integrated as a unit.

Further, it is characterized in that the “inner device” is transferredupward in the sealed vessel 3000 when source materials are supplied intothe crucible 10, and when a manufactured GaN crystal is taken out fromthe crucible 10. Then, in the following, the present embodiment ismainly explained based on the differences between the present embodimentand the first and the second embodiments, and when identical or similarsymbols for previously explained component parts are used, descriptionsfor such symbols in the first and second embodiments are simplified oromitted (see FIG. 17A-FIG. 17D).

The sealed vessel 3000 includes an upper vessel part 3001 and a lowervessel part 1001.

The upper vessel part 3001 includes a flange part 1003 and is connectedwith the lower vessel part 1001 using a number of bolts 1007B. The innerdiameter of the flange part 1003 has a size that allows passing the“inner device.”

The upper vessel part 3001, as an example shown in FIG. 18, is providedwith three pairs of gloves (3005A, 3005B, 3005C). It should be notedthat the number of gloves and their locations are not limited by thepresent embodiment.

Further, the upper vessel part 3001 includes a source material storagechamber 580 storing metallic Na and metallic Ga, and a crystal storagechamber 590 for storing manufactured GaN crystals. Further, the sourcematerial storage chamber 580 includes a mechanism that allows supplyingsource materials into the source material storage chamber 580 from theoutside of the sealed vessel 3000 without affecting the atmosphere inthe sealed vessel 3000. The crystal storage chamber 590 includes amechanism that allows taking a GaN crystal stored in the crystal storagechamber 590 out of the sealed vessel 3000 without affecting theatmosphere in the sealed vessel 3000.

Further, the upper vessel part 3001 can be supplied with additionalnitrogen gas when necessary for maintaining its internal pressure to beslightly higher than the atmospheric pressure.

The gas purification apparatus 3002 is connected to the upper vesselpart 3001 through two pipes (3003, 3004). Thereby, impurities that arecontained in the space of the upper vessel part 3001 are removed.

The lower vessel part 1001 can separate a base part 1002 by removing anumber of bolts 1007A. The base part 1002 is penetrated by gas supplyingtubes (1006, 2001), an evacuating tube 1008, power cables (not shown)for heaters, and lead wires (not shown) of thermocouples for temperaturemonitoring, while maintaining their seals. Further, the gas supplyingtube 2001 has flexibility of expansion and contraction to follow thetransferring of the “inner device.”

The inner space of the lower vessel part 1001 can be separated from theinner space of the upper vessel part 3001 by using a flange 1004 and alid 1005. The flange 1004, having a smaller internal diameter than theflange part 1003, is connected to the flange part 1003 with a number ofbolts 1007C.

The lid 1005 is fixed to the loading device 3010 in the sealed vessel3000. For the loading device 3010, one end is connected to the lid 1005and another end includes a wire connected to a reel, with a motorturning the reel. Thus, the “inner device” can be transferred up anddown by using the loading device 3010.

The sealed space, formed by the lower vessel part 1001, the flange part1003, the flange 1004, and the lid 1005, is made for a pressureresistance to over 100 atmospheres.

Thus, a pressure-resistant vessel can be comprised of the lower vesselpart 1001, the flange part 1003, the flange 1004, and the lid 1005.Further the lower vessel part 1001, the flange 1003, the flange 1004,and the lid 1005 are water cooled. Pressure resistance is not necessaryfor the upper vessel part 3001.

The connection of the sealed vessel 3000 using the bolts is performedthrough a resin O-ring.

The reaction vessel 20 includes a body part 2002 accommodating thecrucible 10, a tube extension part 2004, and a lid part 2005.

The lower part of the tube extension part 2004 is connected to the bodypart 2002 through the flange 2003 with plural bolts 2008A and 2008B. Theupper part of tube extension part 2004 is connected to the lid part 2005with plural bolts 2008C. The tube extension part 2004 includes a bellowsfunction and is flexible.

A gas supplying tube 2001 is connected to the bottom of the body part2002, which allows introducing gas into the reaction vessel 20.

The reaction vessel 20 is held with a hanging part 2011. The hangingpart 2011 is fixed on the flange 1004. Thereby, this provides forlong-time reliability of the device because there is no mechanicalinterference with other parts due to thermal expansion or thermalshrinkage due to rising temperature or falling temperature of thedevice.

Further, the bolt connection of the reaction vessel 20 is made with ametallic O-ring.

The pressures of the inner part and the outside of the reaction vesselare controlled to be almost balanced through the gas supplying tubes(1006, 2001). Thereby, the reaction vessel 20 need not be pressureresistant and can be constructed with a thin wall metallic vessel.

Manufacturing Method of GaN Crystal

(3-1) By using gloves provided in the sealed vessel 3000, remove all thebolts 1007C in the sealed vessel 3000.

(3-2) With the loading device 3010, transfer the lid 1005 upward.Thereby, the “inner device” is transferred upward inside the sealedvessel 3000 (see FIG. 19). The loading device 3010 stops when the lid1005 reaches the predetermined position. This position is named “asecond position.”

(3-3) Remove all the bolts 2008A in the sealed vessel 3000, and removethe tube extension part 2004 and the holding device 40 with the lid part2005 (see FIG. 20).

(3-4) Take out the metallic Na and metallic Ga from the source storagechamber, and supply them into the crucible 10 with a mixing ratio 1:1.Further, fix the seed crystal 5 onto the one end of the holding device40.

(3-5) Attach the tube extension part 2004 to the holding device 40 withthe lid part 2005, and connect them with the bolts 2008.

(3-6) Transfer the lid 1005 downward with the loading device 3010.Thereby, the “inner device” is transferred downward. The loading device3010 stops when the lid 1005 reaches a predetermined position. Then,this position is named “a first position.”

(3-7) Connect the flange 1004 and the flange part 1003 with the bolts1007C.

(3-8) Perform the same operations as the above steps of S4-S11sequentially.

(3-9) Perform the above operations (3-1)-(3-3) when the temperatures ofthe crucible 10 and the reaction vessel 20 become room temperature

(3-10) Take the manufactured GaN crystal out from the crucible 10, andstore it in the crystal storage chamber (not shown).

(3-11) Perform the same operations (3-4)-(3-7) above, make preparationsfor the succeeding GaN crystal manufacturing.

(3-12) Perform the same operations (3-8)-(3-10) above, and manufacture aGaN crystal.

In the following, repeat the same operations (3-11) and (3-12) whennecessary.

As explained above, for the crystal manufacturing apparatus 100C relatedto the present embodiment 3, the “gas supplying device” is comprised ofthe gas supplying tube 90 and the pressure control device 120.

Further, the “operational method” is comprised of using three pair ofgloves (3005A, 3005B, and 3005C).

Further, the “transferring mechanism” is provided with the loadingdevice 3010.

As explained above, according to the crystal manufacturing apparatus100C related to the present embodiment 3, the “inner device” istransferred upward by using the loading device 3010 in the sealed vessel3000 with a nitrogen gas atmosphere, and using the gloves providessupplying source materials (metallic Ga and metallic Na) into thecrucible 10 and taking out the manufactured GaN crystal from thecrucible 10. Thereby, manufacturing GaN can be performed whileprotecting the “inner device” from being exposed to air. Thus, a similareffect of the above first embodiment can be obtained by the presentembodiment.

Fourth Embodiment

A fourth embodiment of the present invention is explained by referringto FIG. 21. FIG. 21 shows a schematic diagram of a crystal manufacturingsystem related to the fourth embodiment of the present invention.

The present crystal manufacturing system comprises a source materialvessel 800 and plural crystal manufacturing apparatuses (810, 820, 830,840, and 850). The source material vessel 800 has a plane pentagon shapeand accommodates metallic Ga and metallic Na in it.

Each crystal manufacturing apparatus is equivalent to any of the abovecrystal manufacturing apparatuses 100, 100A, 100B, or 100C. Further, foreach crystal manufacturing apparatus, by using gloves provided in theapparatus, metallic Ga and metallic Na can be taken from the sourcematerial vessel 800 and be supplied them the individual crucible, almostwithout changing the atmosphere in the sealed vessel.

According to the crystal manufacturing system related to the fourthembodiment, as GaN crystals are manufactured by plural crystalmanufacturing apparatuses independently, so that the mass productivityof crystal manufacturing can be increased.

Although the present fourth embodiment has explained an example of thecrystal manufacturing system having five crystal manufacturingapparatuses, the present invention is not limited to this embodiment,but various variations and modifications may be made without departingfrom the scope of the present invention. More generally, the system iscomprised of a source material vessel with an n-sided polygon (n is aninteger, n≧3) with n crystal manufacturing apparatuses connected to thesource material vessel. In the present case, the source material vesselmay have a regular n-sided polygon shape or a non-regular n-sidedpolygon shape.

In individual embodiments above, although it has explained for thecrystal growth temperature at 800° C., it is not limited to theembodiments, as the crystal growth temperature may be a temperaturebelonging to the region REG3 in FIG. 9. Further, the nitrogen gaspressure in the reaction vessel 20 may be a pressure belonging to thesame region (region REG3) of the crystal growth temperature.

In the embodiments above, it has explained that a GaN crystal ismanufactured based on the seed crystal growth. It is not limited to theembodiments, but GaN crystals may be manufactured by using multiplenucleation growth caused by multiple nucleation generation of GaNcrystals instead of the seed crystal growth. In such case, the crystalgrowth temperature may be a temperature that belongs to the region REG2shown in FIG. 9. Further, the nitrogen gas pressure in the reactionvessel 20 may belong to a pressure at the same region (region REG2) as apressure of crystal growth temperature.

In each embodiment above, the oscillation device 230, the up/downmechanism 240, and the oscillation detecting device 250 may be omitted.Even in this case, GaN crystals can be manufactured without exposing the“inner device” to air.

Further, for each embodiment, the piping 180, the thermocouple 190, thegas supplying tube 200, the flow meter 210, and the gas cylinder 220 canbe omitted. Even this case, GaN crystals can be manufactured withoutexposing the “inner device” to air.

Further, for each embodiment, the piping 180, the thermocouple 190, thegas supplying tube 200, the flow meter 210, the gas cylinder 220, theoscillation device 230, the up/down mechanism 240, and the oscillationdetecting device 250 may be omitted. Even this case, GaN crystals can bemanufactured without exposing the “inner device” to air.

For each embodiment above, although it has explained that supplyingmetallic Na and metallic Ga into the crucible 10 is performed in anitrogen gas atmosphere, the present invention is not limited to thatembodiment. Metallic Na and metallic Ga may be supplied into thecrucible 10 in an atmosphere of an inert gas, such as Ar, He, Ne or Kr.In that case, it is preferable that the amount of moisture contained inthe inert gas or nitrogen gas be below 1 ppm, and the amount of oxygencontained in the inert gas or nitrogen gas be below 1 ppm.

Further, for individual embodiments above, although it has beenexplained that the mixed molten liquid 270 comprises metallic Na andmetallic Ga, the present invention is not limited to the embodiment.Instead of Na, an alkali metal, such as lithium (Li), or potassium (K)or an alkaline earth metal, such as magnesium (Mg), calcium (Ca), orstrontium (Sr) may be used. Further, instead of Ga, a group III metal,such as boron (B), aluminum (Al), or indium (In) may be used. Thus amixed molten liquid made of a Group III metal (including boron) andalkali metal or alkaline earth metal may be used.

For individual embodiments above, instead of nitrogen gas, a compoundcontaining nitrogen as a constituent element in it, such as sodium azideand ammonia may be used.

The group III nitride crystal, manufactured by using a crystalmanufacturing apparatus related to the individual embodiments above, isused for fabricating Group III nitride semiconductor devices, such aslight emitting diodes, semiconductor lasers, photodiodes, andtransistors.

Further, the present invention is not limited to these embodiments, butvarious variations and modifications may be made without departing fromthe scope of the present invention.

As explained above, according to the embodiments of the crystalmanufacturing apparatus of the present invention, it is preferable toperform Group III nitride crystal manufacturing without exposing partsinside of the outer vessel to air and to avoid removing an inner vesseland the like.

The present application is based on Japanese Priority Application No.2007-056859 filed on Mar. 7, 2007, and Japanese Priority Application No.2007-320289 filed on Dec. 12, 2007 with the Japanese Patent Office, theentire contents of which are hereby incorporated herein by reference.

1. A crystal manufacturing apparatus for manufacturing a group IIInitride crystal, comprising: a crucible that holds a mixed molten liquidincluding an alkali metal and a group III metal; a reaction vesselaccommodating the crucible in the reaction vessel; a heating device thatheats the crucible with the reaction vessel; a holding vessel having alid that is capable of opening and closing, accommodating the reactionvessel and the heating device in the holding vessel; a sealed vesselaccommodating the holding vessel in the sealed vessel, having anoperating device that enables opening the lid of the holding vessel forsupplying source materials into the crucible and taking out amanufactured GaN crystal under a sealed condition, and closing the lidof the holding vessel that is sealed in the sealed vessel, the sealedvessel including an inert gas atmosphere or a nitrogen atmosphere in thesealed vessel; and a gas supplying device for supplying a nitrogen gasto the mixed molten liquid through each of the vessels.
 2. A crystalmanufacturing apparatus for manufacturing a group III nitride crystal,comprising: a crucible that holds a mixed molten liquid that includes analkali metal and a group III metal; a reaction vessel accommodating thecrucible in the reaction vessel; a heating device that is positioned ata predetermined location relative to the crucible, and heats thecrucible through the reaction vessel; a sealed vessel accommodating thereaction vessel in the sealed vessel, having an operating device thatenables opening a lid of the reaction vessel for supplying sourcematerials into the crucible and taking out a manufactured GaN crystalunder a sealed condition, and closing the lid of the reaction vesselthat is sealed in the sealed vessel, the sealed vessel including aninert gas atmosphere or a nitrogen atmosphere in the sealed vessel; agas supplying device for supplying a nitrogen gas to the mixed moltenliquid through each of the vessels; and a transfer mechanism that allowsfor the sealed vessel to be transferred relative to the reaction vesseland the heating device, or the reaction vessel and the heating device tobe transferred relative to the sealed vessel, wherein the relativeposition between the reaction vessel and the heating device ismaintained, and the transfer mechanism provides for the reaction vesselin the sealed vessel to be positioned at a first position when crystalgrowth is performed, and the reaction vessel in the sealed vessel to bepositioned at a second position which is different from the firstposition when the source materials are being supplied or the group IIIcrystal is being taken out.
 3. The crystal manufacturing apparatusaccording to claim 2, further comprising: a stage in the sealed vesselfor loading the reaction vessel and the heating device, wherein thetransfer mechanism provides for a position of the stage being changedrelative to the sealed vessel during the transferring.
 4. The crystalmanufacturing apparatus according to claim 3, wherein an inner space ofthe sealed vessel is separated into two inner spaces by the stage. 5.The crystal manufacturing apparatus according to claim 4, furthercomprising a pressure control device for controlling the pressures inthe two inner spaces to be equally balanced while the stage is beingtransferred.
 6. The crystal manufacturing apparatus according to claims1, wherein the sealed vessel further comprises a source material storagechamber for storing the source materials and a crystal storage chamberfor storing a manufactured group III nitride crystal.
 7. The crystalmanufacturing apparatus according to claim 6, wherein the sourcematerial storage chamber further comprises a supplement mechanism thatis capable of supplying source materials into the source materialstorage chamber from the outside of the sealed vessel without changingthe atmosphere in the sealed vessel.
 8. The crystal manufacturingapparatus according to claim 6, further comprising a take-out mechanismthat is capable of taking out a group III crystal stored in the crystalstorage chamber to the outside of the sealed vessel without changing theatmosphere in the sealed vessel.